Optical coherence tomography (OCT) has developed to become an important noninvasive diagnostic technique on the eye. Increasingly, this method is also incorporated into the operative process. OCT allows slice or volume images of the anterior and posterior eye portions to be produced with a comparatively high resolution and virtually in real time.
An example for the frequent use of OCT in the posterior eye portion is the diagnosis of glaucoma, changes in the macula and retinal disorders. By way of example, OCT is applied in the anterior eye portion for pre-, intra- and post-operative diagnostics in the case of cataract operations.
The multifaceted possibilities for using OCT systems have led to the development of optical systems which have both a microscopy system and an OCT system integrated therein. Such systems permit OCT analysis in the field of view of the microscopy system such that the surgeon may navigate the OCT scanning region with the aid of the microscopy system. The produced OCT images may improve intraoperative orientation and diagnostics for the surgeon and therefore ensure an ideal course of the operation.
Typically, such optical systems may be operated in two configurations, with the first configuration serving to examine the anterior portion of the eye and the second configuration serving to examine the retina. In the second configuration, an additional optical assembly is usually arranged between the objective and the eye in the beam path of the microscope and of the OCT system.
In typical systems, this optical assembly is a fundus imaging system or a contact lens. A fundus imaging system consists of an ophthalmoscopy lens and a reducing lens. An intermediate image of the retina is produced between the reducing lens and the ophthalmoscopy lens by way of the ophthalmoscopy lens. With the aid of a positioning device, it is possible to position the ophthalmoscopy lens in such a way that the fundus of the eye is imaged sharply. In particular, fundus imaging systems are disadvantageous in that an unwanted eye contact by the ophthalmoscopy lens may occur during the operation. Moreover, options for illuminating the operating field by means of illumination from the operating microscope are greatly restricted when the fundus imaging system is used. Therefore, the illumination of the microscopy system is usually switched off in the case of operations in the posterior portion.
In contrast thereto, contact lenses are affixed on the cornea with the aid of a contact gel. The contact lens lifts the refractive power of the cornea. This facilitates positioning the object plane of the microscope on the retina by modifying the distance. However, the contact lens may be destabilized during the operation. Air bubbles, blood and liquid may ingress between cornea and contact lens. The consequence is that the surgical intervention has to be interrupted in order to undertake a time-consuming cleaning process.
A complicated re-equipping process is required both in the case of fundus imaging systems and in the case of contact lenses in order to change between the configuration for imaging the anterior portion and the configuration for imaging the retina. Moreover, when these systems are used, the object plane of the microscope and the scanning plane of the OCT system together are respectively arranged only in the anterior portion of the eye or only in the posterior portion of the eye. However, there are surgical interventions in which it has been found to be advantageous that an examination of the retina by means of OCT is required, but wherein the anterior portion of the eye should continue to be observed by the microscopy system. A cataract operation is an example of such a surgical intervention.
There is therefore a need for optical systems which facilitate efficient and precise carrying out of an examination or intervention on the eye.